Rotary tube furnace



4 SheetsSheet l C. P. DEBUCH ROTARY TUBE FURNACE Filed Nov. 9, 1932 Dec.8, 1936; c. P. DEBUCH ROTARY TUBE FURNACE Filed Nov. 9, 1952 4Sheets-Sheet 2 8, 1936. c. P. DEBUCH ROTARY TUBE FURNACE Filed Nov. 9,1932 4 Sheets-Sheet 5 Dec. 8, 1936. c DE 2,063,233

ROTARY TUBE FURNACE Patented Dec. 8, 1936 UNITED STATES ROTARY TUBEFURNACE Carl Paul Dbuch, Frankfort-on-the-Main, Germany, assignor toAmerican Lurgi Corporation, New York, N. Y., a corporation of New YorkApplication November 9, 1932, Serial No. 641,935 In Germany July 6, 1931Claims.

This invention relates to rotary-tube furnaces.

Up to the present, the application of the rotarytube furnace has beenrestricted to a comparatively small number of uses, probably the chiefreason for this being that, with the known rotary-tube furnaces, thetemperature in every part of the furnace cannot be controlled. As arule, the air of combustion is admitted into the rotary furnace at oneend, and, in most instances, the burners also are situated at that end.Accordingly, the temperatures are highest at that end, and often attainundesirable peaks, while the other end of the furnace usually suffersfrom lack of heat.

. For many purposes this operative condition is harmless, and indeedoften desirable. In many other instances, however, it is a drawbackwhich cannot be counterbalanced even by the valuable special propertiesof the rotary furnace, such as the possibility of continuous operation,the highly effective intermixing of the materials under treatment, andso forth.

Rotary-tube furnaces are also known in which the nozzles supplying thefuel are disposed at right angles to the axis of the drum and nozzleblocks are passed through the shell of the drum.

Rotary-tube furnaces have also been heated by flameless surfacecombustion, the wallor parts thereofof the drum being made of materialpervious to gases, and a mixture of combustible gas and air beingforced, from a distributor head at the end of the furnace, into passageslocated in the furnace wall, from which it passes into the perviousfurnace lining.

These arrangements, however, do not enable the temperature of the chargematerial to be adjusted to a uniform level throughout all parts of thefurnace, since if merely the fuel be admitted through nozzles intovarious parts of the furnace,

high temperatures are generated in the vicinity of the streams of fuel,thust giving rise to the danger of the charge becoming overheated insuch localities. The same defect attaches to heating the furnace wall byflameless surface combustion, since the heated parts attain very hightemperatures which are transmitted to the portions of the charge thatare in immediate contact with those portions of the furnace wall. Thesemethods of heating have accordingly been employed only in cases wherespecially high temperatures were desired in individual zones of thefurnace. In carrying out roasting processes according to another knownmethod, pulverulent sulphidic ore is blown into the furnace, throughnozzles, at a point near the discharge end, in order to stimulate thereaction which otherwise becomes more sluggish towards the finish. Sucha method of regulating the temperature, though practicable, isnevertheless extremely defective. The injected material not only comesinto action at the point of introduction, but is seized upon by thegases and distributed over a wider zone of the furnace. This measure istherefore of value only where longer zones inside the furnace are to beinfluenced. The defect that the actual heating of the furnace takesplace at one end, and that danger- 5 ous peak temperatures are generatedin the vicinity of that end, still remains as such.

These aforesaid drawbacks are obviated by the present invention, whichenables the temperature to be modified at convenience in any point ofthe furnace and at any time while the furnace is running. In particular,it enables a uniform temperature to be maintained throughout thefurnace. With this object, according to the in vention, the rotary-tubefurnace is provided with burners which pass through the furnace shelland are distributed over its entire length and periphery. In order toensure continuous control of the supply of fuel and air, the requisitepipes for such supply are located outside of, but integrally connectedwith, the furnace. They are fed by adistributor head situated at one endof the furnace, and each burner can now be adjusted, at any time, asconvenient, so that the working condition of the furnace is completelyunder control. According to the invention, the burners themselvesproject into the interior of the furnace to a point at which they arenot covered up by the layer of charge material. Consequently, thecombustion cannot be obstructed by the movement of the chargeas would bethe case in heating by flameless surface combustion or in admitting thefuel alone through the furnace shelland, above all, there is no localoverheating of the charge through direct contact with the burner flame.

The advantage provided by the invention may be illustrated by anexample.

In caustically burning magnesite temperatures of 900 C. must not beexceeded, since at higher temperatures the caustically burned magnesitebecomes dead-burnt, which greatly reduces its value. In the existingfurnaces, heated from one end and in which the burning temperature hasto be generated by a burner situated on one side, it is impossible toprevent the permissible temperature from being exceeded in that part ofthe furnace that is nearest the burner. The case is different when thefurnace is heated in accordance with the invention. By suitablymanipulating the burners the material freshly charged into the furnacecan be quickly preheated to the burning temperature, and thistemperature can be uniformly maintained throughout the whole length ofthe furnace.

To continue with the example, it is possible, in this manner, whenburning magnesite, to maintain a temperature of 800 C. all along thefurnace, that is to say, to render the whole interior of the furnaceavailable for the causticizing process.

The supply conduits for fuel, air of combustion,

inert or reducing gases and other fluid media to be admitted into therotary furnace can be connected to the distributing pipes of the furnaceby; means of connection members which are disposed concentrically withthe axis of the rotary furnace, the junctions between the rotary andfixed conduits for the fluid media being fitted with stuffing boxes.

At the seat of the connection, a rotary member is concentrically fittedin or over a fixed member, and the stuffing box for preventing theescape of the medium flowing through the two members, is insertedbetween their facing peripheral surfaces. When stuffing boxes are used,however, wear of the surfaces and packing means is inevitable in thelong run, and repacking is required at intervals.

For this reason a special connecting means, which is not attended withthis drawback, is preferred for the rotary furnace according to thepresent invention. At the points of attachment, the lengths of piping tobe connected together are provided with metallic surfaces disposed atright angles or obliquely to the rotational axis of the furnace. Thesesurfaces are in direct sliding contact and are pressed together withsufficient force to produce the desired impermeability to gas orliquids.

The specific superficial pressure on they joint does not, however, needto be very high, a slight excess over the pressure exerted by the fluidmedium being sufficient. The surfaces in sliding contact work themselvesprogressively into more intimate contact during use, so that thetightness of the joint is never endangered. Even the penetration ofdust, or similar fine solid substances, between the packing surfaces isin no wise injurious because, at the worst, they merely increase thewear of the contact surfaces and, as experience has shown, the amount ofsuch wear is small even under unfavourable conditions. It does notaffect the efficiency of the packing, since, in all cases, one of themembers to be connected can easily be arranged so as to slide in thelongitudinal direction of the rotational axis. There is also nodifficulty in arranging for the establishment and maintenance of thenecessary contact pressure. For example, the fixed member can be pressedagainst the rotary member by the aid of springs, inserted between theformer and fixed abutments. The same effect can also be obtained by thetension of a cord. The abutment needed in any event can also be providedon the rotary member. 7

The sliding-contact metallic surfaces may be formed by machining thecorresponding parts of the connections. In many cases, however, it maybe advisable to insert special rings, to take up the wear, between thetwo members to be connected, in which event a certain amount of play mayexist between the two members, so that the intermediate member does notneed renewal until partly worn away. In such case, the surfaces of thepacking that are in sliding contact are not necessarily planar. On thecontrary, the connections may be so designed that the packing surfacesin mutual contact are of labyrinthine pattern, the number of theserrations depending on the conditions the device has to meet in respectof pressure, rotational velocity and so forth.

Where a plurality of rotary and fixed pipes are to be simultaneouslyconnected together, both these members and the packing devices aredisposed concentrically to one another and to the axis of the furnace,and the packing devices may lie in the same plane, though it is alsopossible to offset them in the direction of the rotational axis.

These connections have behaved so well, in use, that their applicationfor other purposes than those of the rotary furnace according to theinvention appears to be suitable, for example for making gasorliquid-tight connections on revolving pipes or vessels (such as rotaryautoclaves), or vessels equipped with stirrers, and also for blowers andpumps.

As already mentioned, in the case of burners fitted to the rotaryfurnace according to the invention, the burner nozzle must extend so farinto the interior of the furnace that it cannot be covered over by thecharge material in the furnace. The burner nozzle is carried, forexample, on a stem which projects, through the furnace wall, to asufficient distance inside the furnace chamber.

The nozzle and stem are preferably provided with artificial coolingmeans, and the cooling medium may consist, for example of the air ofcombustion, which is preheated at the same time, after which it can bemixed with the fuel and the mixture then passed to the burner.

According to the invention, the burner can also be arranged in such amanner that, when it is temporarily shut off, the cooling medium can,nevertheless, be led away, for example, to be discharged, after use,into the open air instead of into the furnace.

Burners of this type possess noteworthy advantages in respect of flameformation and flame development, which can always be adjusted to theoptimum condition by means of the now possible convenient adjustment ofthe distance between the burner nozzle and the furnace wall, and of theburner stem and the like.

The bore of the burner can be fitted with a baflie, which sets up apowerful whirling motion, by which the fuel and air of combustion areintermingled, in known manner. This baflle has a central bore, so as notto hinder observation of the flame.

In order more clearly to understand the nature of the invention,reference is made to the accompanying drawings, which illustratediagrammatically an embodiment of the furnace and in burners 2,distributed over the length and perima.

eter of the furnace and projecting through the furnace shell. The fueland air of combustion are supplied to the burners, from a fixed pipe 5and distributor head 5, through the pipes 4 and 4a, which are locatedoutside the furnace and turn with it. In this furnace, the usual heatingfrom the end is dispensed with entirely. The introduction of the chargeis indicated by an arrow. The opposite end is completely closed. Each ofthe burners can be regulated, and turned on and off independently, bythe members 3.

Fig. 2 represents an embodiment of a distributor head, in which the fuel(such as producer gas) and the air of combustion are supplied separatelyand are passedalso separately--to the nozzles by way of the pipes 4 and4a. The arrow I indicates the course of the gas, and arrow 8 that of theair of combustion. The gas-tight connection between the fixed supplypipes I I and I2 and the rotating pipes I4 and I3, situated in thecentral axis of the furnace, is obtained by means of the stufiing boxes9 and I0.

Fig. 3 shows another embodiment of a distributor head, in which the gasand air are also supplied to the distributor head through the branches Iand I6. They are mixed in the chamber I1 and pass, in the condition ofmixture, through the branches I8 and I8a into the pipes leading to theburners. There is no need to point out that, with slight modifications,solid or liquid fuel can be mixed with the air of combustion in adistributor head of this type. The supply can be regulated by means ofthe circular slide I9, which is provided with oblique slots and isadjustable by means of the lever 20.

In these distributor heads, the stuffing-box packings may also bereplaced by the packing devices of the present invention, the principleof which is illustrated in Figs. 6 to 8.

In Fig. 6, is the rotary and 26 the stationary member of a connection,26 being for example, the wall of a stationary gas pipe and 25 the wallof a rotary gas pipe, which is to be connected to the former and rotatesabout the axis of the pipe. The end face of the pipe 25 is provided withthe annular projection 21, and the end face of 26 with a groove 28fitting said projection. The end face of the projection 2'! is pressedso firmly against the bottom of the groove by an annular projection 21provided on the other member.

According to- Fig. 7, a carefully machined ring 29, of high-gradematerial and intended to take up the wear, is inserted in an annulargroove in one of the members of the joint and is pressed against thebottom of the groove by an annular projection 21 provided on the othermember.

Fig. 8 shows how the requisite contact pressure is obtained by means ofa screw cap 30 and the springs BI, so that a relatively heavy pressureis set up between the cap 30 and the actual packing ring 32 rotating inrelation to the latter. In order tolessen the friction between thepacking ring and screw cap, a ball bearing 33 is inserted between them.A plurality of packing joints 34 and 35 can be disposed concentrically.

Figs. 9, 10 and 15 show the application of such packing devices to adistributor head of the rotary furnace according to the invention. 36 isthe rotary member (mounted on and rotating with the furnace) of thedistributor head, and 31 is the fixed member of the latter. 38a-c arethree feed pipes for fluid media, such as combustible and incombustiblegases, and also air. 39ct-f are the delivery pipes conveying the fluidmedia from the distributor head to the places of their employment in thefurnace. Each of these feed pipes can be connected with a plurality ofdelivery pipes, as shown in Figs. 11 and 12. 43 are the packing devicesat the points of junction of the several concentric pipes. In theembodiment according to Fig. 15, the fixed member 3'! is pressed againstthe member 36, which turns with the furnace M, by the tension of a cordand the weight 42.

According to .Figs. 9 and 10, the contact pressure is produced bysprings 43.

Fig. 9 shows, on a larger scale, the actual joint according to Fig. 10.

The action of the burner according to Fig. 4 is based, in known manner,on the gas being fed (at 23) to the burner from a distributor pipe (notshown) under such a high pressure that the air of combustion isautomatically drawn in (at 24) from the surrounding atmosphere by theeffort of suction. According to Fig. 4, 44 represents the inlet portionof the burner, which element is situated outside of the furnace and isattached to the furnace wall by means of a flange 45. Ports 24, in inletportion 44, admit atmospheric air into the burner. Connected to thisintake member 44 is the burner stem BI surrounded by the insertionmember 41. Gaseous fuel fed, at 23, to the burner under pressure entersthe burner by way of the gas intake portion 62 which latter is attachedto the inlet portion 44, communicating therewith through the opening 63.Adjustment of the rate of admission of gas to the burner is madepossible through the agency of the adjustable hollow closure tube 64which may be seated in opening 63. 5'1 represents a peephole cap at theouter end of tube 64, and 58a is a handwheel for adjusting the positionof tube 64 with respect to opening 63. In the burner according to Fig.5, fuel and air are supplied separately, under pressurefor example bythe aid of the distributor head shown in Fig. 2-and are not mixed untilthey reach the burner head.

So-called jet blocks, known per se, can also be employed as burners,since, in such case, the supply of fuel and air can also be accuratelyregulated by the devices according to the invention. Such burners arealso arranged, in a similar manner to those according to Figs. 4 and 5,so as to project through the charge material in the furnace.

Another gas burner is shown, in burning position, in Fig. 13, and incooling position in Fig. 14. The burner consists of the intake portion44, which is situated outside the furnace and is attached to the furnacewall by means of a flange 45 in the usual manner. Connected with thisintake 44 is the burner stem 46, surrounded by the insertion member 41.The burner nozzle 48 is. seated on the stem. These three members of theburner are made separately and assembled to form the complete burner, sothat, in the event of wear of any of the parts they can be replacedindependently of the rest.

The fuel, such as gas or oil, flows from the connection pipe through thesupply pipe 49 into the pipe 50, which is preferably arranged centrally.The corresponding air is admitted into the annular chamber 52 of theburner member 44 through the branch 5|. It then passes through pipes 53(of any suitable number) to near the free end of the stem 46 and thenback through the annular space 54 formed by the burner stem 46 and thepipe 50. In this manner, an intensive cooling of the stem 46 and nozzle48 is produced. Finally, the air enters, through the uniformlydistributed peripheral openings 55, into the pipe 50, where it mixeswith the fuel, such as gas. In order to obtain a more intimate mixing,the pipe 56 is provided with an internal bafile ring 56 which sets thefuel mixture in vortical motion, the mixture being then ignited andburned in the nozzle 48.

The nozzle 48 is of ceramic material or metal and is screwed into theburner stem 46. This arrangement enables, on the one hand, nozzles ofvarious shapes to be inserted and the form of the flame to be modified,while, on the other hand, these nozzles can be easily replaced in theevent of damage from any cause. The cross-sectional ratios of the pipe50 and nozzle 48 are so calculated that the rate of flow of the fuelmixture in the pipe 50 exceeds the velocity of ignition. According tothe amount of the supply, the rate of flow in the flared bore of theburner nozzle 48 sooner or later becomes equal to the velocity ofignition, so that the flame burns at a point more or less remote fromthe orifice of the nozzle. If, from any cause, the flame back fires, thebaffle 56 soon becomes red hot, since the development of the flame thencommences in the pipe 50. The incandescence of the baffle or of a stayon which it is carried, or also of a second stay that can be disposed ata suitable point in the pipe 50, can be easily observed through apeephole 51, so that remedial measures can be adopted at once. Thebaffle 55 therefore discharges a dual function. On the one hand, itthoroughly intermingles the fuel mixture, under normal workingconditions, and on the other, the baflle, or its supporting stay, glowswhen the burner lights back, and thus reveals a change in the combustionprocess in the burner. Finally, said baffle, being perforated, does notprevent the charge in the furnace from being observedaccording to theposition of the burner, or the furnacethrough the peephole 51. vIf, forany reason, the burner is not in use,or temporarily out of usewhile thefurnace is running, it might possibly become damaged by the hotatmosphere of the furnace. According to the present invention, undersuch conditions, the fuel supply alone is shut off, for example by athrottle member in the supply pipe. Moreover, by turning the handwheel58 (as shown in Fig. 14), the valve plate 59 on the gas supply pipe 49is pushed forward so as to close the pipe 50. The aircontinues to takethe same course as when the burner is in operation, as far as to theintake slots 55, from which point, however, it now passes off into theatmosphere through openings 60 in the intake member 44. This arrangementassures the air acting solely as cooling medium and being prevented fromentering the furnace.

Of course, even in that position of the bumer, the fuel, such as gas,can still be admitted into the furnace so that it can react with theatmosphere or charge in the furnace.

If, for any reason, the burner is to be detached from the furnace-forexample for changing the nozzle 48-this can be very easily effected,according to the present invention, without fear of affecting thedurability of the furnace masonry, since the firmness of the masonry isensured by the insertion member 41. This latter also performs thefunction of protecting the burner stem 46 from mechanical attack by thefurnace charge when the furnace is running. This member 41 is preferablyof highly refractory material.

This arrangement enables the feed to the burners to be varied atconvenience and also any convenient number of burners to be kept in, orput out of, operation in the same furnace.

I claim:

1. Device for the introduction of fluid agents into a rotary tubularfurnace comprising, in combination, a cylindrical chamber located at oneend wall of the rotary tubular furnace its walls revolving with therotary tubular furnace and its side walls being concentric with thefurnace axis; at least one pipe connecting said chamber with at leastone passage in the shell of the rotary tubular furnace and revolvingwith the rotary tubular furnace; a stationary feed pipe for the fluidagent opening into said chamber and having metallic end surfaces at itsend towards the furnace these end surfaces engaging the end surfaces ofthe cylindrical walls of said chamber, and means for pressing the endsurfaces of said stationary feed pipe hermetically against the endsurfaces of the revolving walls of said chamber, the end surfaces ofsaid chamber and of said feed pipe engaging each other with packinggrooves and tenons in the section through the axis of the furnace, ametallic ring being positioned in at least one of said grooves.

2. Device according to claim 1, in which the metallic ring is awear-resistant steel ring.

3. Device for the introduction of fluid agents into a rotary tubularfurnace comprising, in combination, a plurality of cylindrical chamberslocated at one end wall of the rotary tubular furnace their wallsrevolving with the rotary tubular furnace and their side walls beingconcentric with each other and with the axis of the furnace; at leastone pipe connecting each chamber with at least one passage in the wallsof the rotary tubular furnace and revolving with the rotary tubularfurnace; a plurality of stationary feed pipes forfiuid agents openinginto each chamber their ends being of annular construction andconcentric to each other and to the axis of rotation of the furnace andhaving metallic surfaces at the ends engaging the end surfaces of thecylinderical walls of said chambers; and means for pressing the endsurfaces of said stationary feed pipes hermetically against the endsurfaces of the revolving walls of said chambers, the end surfaces beinglocated in a plane perpendicular to the axis of the furnace.

4. Fluid tight connection between relatively rotating supply anddistributing pipes for fluid media in which a plurality of concentricsupply pipes communicate with a plurality of concentric distributingpipes by means of metallic end surfaces provided on the supply anddistributing pipes and disposed perpendicularly to the axes of thelatter, said end surfaces providing sliding contacts, said connectionbeing further characterized in that a plurality of separate concentricpassages are provided for the separate movement of a plurality of fluidstreams from said supply pipes into said distributing pipes.

5. Device for the introduction of fluid agents into a rotary tubularfurnace, comprising a cylindrical chamber located at one end of therotary tubular furnace, its walls revolving with I the rotary tubularfurnace and its side walls being concentric with the axis of thefurnace; a tube connecting said chamber with at least one passage in thewalls of the rotary tubular furnace and rotating with the rotary tubularfurnace; a plurality of non-rotary feed pipes for fluid agents openinginto the chamber, their ends being of annular construction and lyingconcentric to each other and to the axis of rotation of the furnace,with metallic end surfaces at the ends that fit on the end surfaces ofthe cylindrical walls of the chamber; means for pressing the endsurfaces of the non-rotating feed pipes airtight against the endsurfaces of the rotary walls of the chamber; and means for introducing aplurality of fluid agents through said nonrotating pipes into saidchamber and there mixing them.

CARL PAUL DEBUCI-I.

Certificate of Correction Patent No. 2,063,233. December 8, 1936.

It is hereby certified that the name of the patentee in the abovenumbered patent was erroneously Written and printed as Carl Paul Dbuchwhereas said name should have been Written and printed as Carl PaulDebuch, as shown by the records of this office; and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the case in the Patent Ofiice.

Signed and sealed this 30th day of March, A. D. 1937.

[SEAL] 7 HENRY VAN ABSDALE, Acting Commissioner of Patents.

